[2023Q3] Cost of Consensus Security: Hardware

Authors

Irene

Creator

Irene

Created

Aug 22, 2023 7:36 AM

Project

Protocol Security

Stage

Graduated from Notebook

• Intro and Result Recap
• Analysis
• Cost of “bribing SPs”
• Cost of “buying sectors”
• Cost of “adding new sectors”
• Comments and Extras

Intro and Result Recap

1. “Bribing SPs”: the attacker convinces existing SPs in the network to run its software for block production for at least 24h, virtually controlling 33% of the power.
2. “Buying sectors”: the attacker convinces existing SPs in the network to sell their sectors until it gets to control 33% of the power.
3. “Adding new sectors”: the attacker is a valid SP in the network and adds sectors in such a way that in a short period, its consensus power reaches the 33% share

Analysis

• Considering only 32GiB sectors
• Storage cost is SC = $0.000715 per day (reference: https://observablehq.com/@protocol/costs-storage)
• 33% of consensus power = 33% of NetworkQAP
• (august 2023) 33% of 23EiB = 7.6 EiB of QAP.
• How many sectors for 7.6 EiB of QAP?
• Let N be the number of sectors, N depends on the fraction y of the sectors that are with (verified) deals,
• y*N*10 + (1-y)*N *32GiB = 0.33*QAP ⇒ N = 0.33 *QAP / (32GiB *(9y+1))
• (y = 0) All are CC sectors, then N = 7.6 EiB / 32GIB = 2.55 10^8 sectors,
• (y = 1) All are with deals, then N = 7.6 EiB / 320GIB = 2.55 10^7 sectors
• Note that today (10th aug 2023) we have 1.3 EiB/32GiB = 4.36 10^7 sectors with verified deals, which represents ~12% of the total sectors .
• So the HDDCost is in the range [$18k, $184k], and we can consider as realist value the one we get for y = 0.12
• ⇒ HDDCost = ⅓ QAP/ (2.08 *32GiB) *SC = $88.4k

• The per EiB cost of 24h HDD security is SC * (1/3) * SectorsPerEiB = $8k.
• SectorsPerEiB = (1024**6) / (32 * 1024**3) = 33,554,432.
• To get to $1B HDD security requires 125,000EiB in RBP.
• Or for the network to be $1B/$88k= 11,346x larger.

Cost of “bribing SPs”

• Estimating the cost of this strategy is not easy since the “price” of bribing may depend on the different SP behaviors. We think that a lower bound for this is considering the HDD cost computed above.
• TODO: add private key bribing - or assume private key is at facility

Cost of “buying sectors”

• In this case, we consider the HDD cost plus the cost of paying to the SP the future earning (block rewards) and finally plus the cost of buying the storage pledge.
• Future earnings (per sector):
• Assume the adversary buys sector with a remaining life of 6 months (on average)
• Per sector:
• 180*BR*, with BR = sector block reward in a day
• SectorBlockReward =EpochReward *SectorQAP/NetworkQAP (per epoch)
• To get to 33% of QAP:
• Cost = (180*EpochPerDay*EpochReward*0.33)*FILPrice
• EpochReward of today is 13FIL, but will go down in the future (see Figure 4A here)
• Assume the attack is performed is Q22024, the we consider a EpochReward of 11FIL
• 180 * 2880 * 11FIL * 0.33 * $4 ~$7.5M
• TODO: better estimate the remaining life!
• Storage pledge:
• Per sector:
• SectorInitialStoragePledge(t) =Estimated 20DaysSectorBlockReward
• SectorBlockReward =EpochReward *SectorQAP/NetworkQAP
• To get to 33% of QAP:
• 20 * EpochPerDay * EpochReward * 0.33 (ie, 20x the reward for 33% of the QAP)
• Epoch reward was higher in the past, so if we consider today value we get a lower bound
• StoragePledgeCost = 20 * 2880 * EpochReward* 0.33 * FilPrice
• 20 * 2880 * 13FIL * 0.33 * $4 = ~$1M

Cost of “adding new sectors”

• How much RBP you need to add to get to 33% of QAP (assuming you add only sectors with verified deals)?
• x is the fraction of existing RBP is with deals,
• QAP = RBP (1-x) + 10*RBP*x
• y is the fraction of RBP (all with 10x power) to be added to get to 33% of QAP
• 1/3 = (10*y*RBP)/NewQAP
• 1/3 = 10*y/ [ (1-x) + 10*x + 10*y)]
• y = 1- x +10x/20

• y*RBP = QAP/20 → 23EiB/20 = 1.15EiB

• Here we need to consider the cost of sealing (performing PC1)
• Per sector: with the latest Supranational improvement, that is around $0.04 per 32GiB sector
• To get to 33% of new QAP:
• 1.15EiB / 32GiB * $0.04 ~$1.54M
• And the gas cost from ProveCommitSector/ProveCommitAggregate
• Resource:https://observablehq.com/@protocol/costs-gas?collection=@protocol/costs
• Per sector (min, using no batching): 0.016
• To get to 33% of new QAP:
• 1.15EiB / 32GiB * 0.016 * $4 ~$2.47M
• TODO:
• Consider a ration for verified deals on the new power
• Correlate onboard with gas price history (consider a discount since we are making gas cheaper)
• Rate limits
• Cost of gas (primarily PSD)
• FIL+

Comments and Extras

• Shut down facilities

• Renting storage

• Include the revenue of the attack!